The stability of railway embankment is essential for safe transport. In order to ensure safe transport, water should be allowed to freely drain. Furthermore, as the engine driver has to be able to see signs, and people working on the embankment are supposed to easily see flaws on the rails to ensure safety for the passing trains, plants should not be allowed to grow on the embankment. In Sweden there are 12 000 kilometers of railway tracks and 25–30 % of them are treated for weed control every year. The Swedish Transport Administration is currently using the pesticide “Roundup Bio” to remove weeds on the embankment. To prevent the dispersal of chemicals to sensitive ecosystems, chemical transport has to be investigated carefully. In this master thesis a transport model for the transport of pesticides has been simulated using the software “GoldSim”. The model have been developed, optimized and controlled by a sensitivity analysis. In addition to this an analysis of worst case scenarios has been tested. The pesticides “Arsenal 250” with the active substance imazapyr and “Roundup Bio” with the active substance glyphosate have been used in the calibrating of the model. The transport model for imazapyr shows a good estimation of the mass of herbicides in the embankment compared to measurements. There is also a good estimation in the groundwater even if the concentration at the beginning of the simulation period is underestimated. The simulation with glyphosate, on the on the other hand, showed very small quantities of both glyphosate and its degradation product AMPA (aminometylphosphateacid) in both the embankment and in the groundwater. The sensitivity test showed that the parameter half-life and Kd-value (adsorption capacity) were the most sensitive parameters in the model. When it comes to the concentration in the groundwater the distance to the groundwater level was the most sensitive parameter, as well as the Kd-value in the embankment, the half-life and the precipitation. As expected, the worst-case analysis showed that a small distance to the groundwater level, a low Kd-value and a short half-life produced even larger concentrations of herbicides in the groundwater. In conclusion it should be mentioned that the stimulation model generally works well in regards to with imazapyr. For stimulation of glyphosate and its metabolite AMPA more work with the model is required for the Swedish Transport Administration to apply it in the future.

A probabilistic risk assessment model using GOLDSIM software was developed to evaluate the uncertainty of selected hydrological and soil parameters on mercury releases from a mercury containment system, which will be constructed within the Environmental Management Waste Management Facility in the Bear Creek Valley at the Oak Ridge Reservation in Tennessee. The main objective was to determine the concentrations and risk of exceeding the drinking water standard of mercury in a selected receptor well. A series of simulations were then conducted for various design periods, with emphasis on 10,000 years to determine those concentrations and risks. Experimental data for selected parameters such as dry bulk density, partition coefficient, and porosity and infiltration rate were represented by Probability Density Functions in support of Monte Carlo analyses. A sensitivity analysis showed that concentrations and risk are, for instance, most sensitive to porosity in the unsaturated zone. The simulations suggest that all herein estimates of concentrations and risks of mercury in drinking water should be well below established limits.

The mining, agricultural and energy sectors, along with the Department of Water Affairs (DWA) are critical role players in managing South Africa’s water resources. Water resources are under increasing pressure due to continuous population growth and economic development. It is critical to adopt a management policy that can lead to sustainable water supply. The National Water Act, 1998, (Act 36 of 1998), Section 56(1) instructs the Minister of Water Affairs to establish a Pricing Strategy for charges for any water use described in Section 21 of the Act. In light of this the Department implemented the Waste Discharge Charge System (WDCS). The WDCS is based on the polluter-pays principle and is focussed on load reduction on order to achieve or maintain resource quality objectives. One of the legal requirements in the mining industry is to have a water use license under Section 21 of the National Water Act of 1998 (South Africa, 1998b) which will lead to the application of the WDCS to the mining industry. This mini-dissertation assesses how the WDCS can be practically implemented from a gold mining perspective. The WDCS require the identification of point and diffuse sources from various pollution sources. A case study was used to determine what information and instruments will be required at a gold mine to implement the WDCS. The determining of the point and diffuse discharges require multidisciplinary studies with the integration of different spheres of the environment. To assist with this a GoldSim model was developed. The main function of the model was to determine the seepage rates per day from pollution sources using the available information. The seepage rates and the water qualities were used to determine the waste loads discharged to the environment. Using the instruments above, a methodology was provided to determine the point and diffuse sources of pollution and calculate the load that will be discharged to the environment which will form the basis of the WDCS. / Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2013

The mining, agricultural and energy sectors, along with the Department of Water Affairs (DWA) are critical role players in managing South Africa’s water resources. Water resources are under increasing pressure due to continuous population growth and economic development. It is critical to adopt a management policy that can lead to sustainable water supply. The National Water Act, 1998, (Act 36 of 1998), Section 56(1) instructs the Minister of Water Affairs to establish a Pricing Strategy for charges for any water use described in Section 21 of the Act. In light of this the Department implemented the Waste Discharge Charge System (WDCS). The WDCS is based on the polluter-pays principle and is focussed on load reduction on order to achieve or maintain resource quality objectives. One of the legal requirements in the mining industry is to have a water use license under Section 21 of the National Water Act of 1998 (South Africa, 1998b) which will lead to the application of the WDCS to the mining industry. This mini-dissertation assesses how the WDCS can be practically implemented from a gold mining perspective. The WDCS require the identification of point and diffuse sources from various pollution sources. A case study was used to determine what information and instruments will be required at a gold mine to implement the WDCS. The determining of the point and diffuse discharges require multidisciplinary studies with the integration of different spheres of the environment. To assist with this a GoldSim model was developed. The main function of the model was to determine the seepage rates per day from pollution sources using the available information. The seepage rates and the water qualities were used to determine the waste loads discharged to the environment. Using the instruments above, a methodology was provided to determine the point and diffuse sources of pollution and calculate the load that will be discharged to the environment which will form the basis of the WDCS. / Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2013

The focus of this work is to investigate the dissolution of MW25, a non-radioactive simulant of UK high-level nuclear waste borosilicate glass, and to predict its performance in the near field of a geological repository. A single-pass flow-through (SPFT) experimental system was used to measure the forward dissolution rates of MW25. Experiments were conducted in two parts. Experiment Part 1 considers the dissolution of the waste glass in deionised water at 40 and 90 oC and circum-neutral pH. Experiment Part 2 considers the dissolution of the waste glass in simulant groundwaters, with similar compositions to groundwaters of Callovo-Oxfordian clay (lower-strength sedimentary rock (LSSR)) and Borrowdale Volcanic Group rocks (higher-strength rock (HSR)), at 40 oC and pH 7. The forward dissolution rate measured in deionised water was found to be approximately one order of magnitude higher at 90 oC than at 40 oC. A similar release was observed for Si, Mg and Al at 40 oC and 90 oC, whereas the B, Cs, Na, Li and Mo showed an order of magnitude increase when the temperature was increased from 40 to 90 oC for low q/S values. The activation energy (Ea) of the reactions shows that the dissolution process is a surface phenomenon. At 90 oC the net effect of the processes governing MW25 dissolution led to the preferential release of boron and alkali metals relative to the release of Si during the transient dissolution stage, accompanied by an increase in the concentration of silicic acid. This suggests that the solution activity of silicic acid at a higher temperature has a weak influence on the release of the mobile elements. The forward dissolution rate measured in LSSR simulant groundwater was found to be slightly higher than that measured in HSR simulant groundwater. The dissolution behaviour of MW25 in both groundwaters is consistent with its behaviour in deionised water at 40 oC, with the dissolution rates of elements increasing as flow rates were increased. However, forward dissolution rates measured in the simulant groundwaters were lower than the forward dissolution rates measured in deionised water under these experimental conditions. This is attributable to the interaction of the components of the simulant groundwaters with the glass, as revealed by post-reaction surface analyses, and a consequential lower alkalinity of the leachates collected in the experiments with simulant groundwater than in deionised water. Reactive chemical transport simulations of waste glass dissolution and radionuclide release in a hypothetical near field were conducted over a time span of a million years with GoldSim. The results showed that enclosing the waste glass in a steel canister covered by a copper canister and emplacing the waste package in a granite host rock is optimal for the long-term isolation of the radionuclides. The waste glass was found to play a significant role in the overall performance of the near field. This study features a new method for estimating the surface area of reacted glass powder more accurately than the geometric surface area estimate, which is the preferred standard method among researchers.